Swarming Squid Sperm: A Strategy in Sneakiness

Sneaky swarming squid sperm. Yeah, let’s talk about that. ‘Cause you hear that and you gotta know, right? But before all the sperm and the swarming is the amorous squid. Let’s start there.

As you may expect, squid have both a male and a female. Male squid produce spermatophores, packets of sperm that they can transfer to the females. Female squid carry around these sperm packets until they are ready to spawn. That can be quite some time in some species. When they are ready, they will use the stored sperm to fertilize and then release hundreds or thousands of eggs into the water as jelly-like strands. That’s about what we know about squid reproduction, the rest is relatively mysterious.

A newish study in Current Biology sheds some light on the mysterious nature of squid sperm. The study organism is Loligo bleekeri, one of the more common of the pencil squids (Loliginidae) in Japan and southern Korea. It is moderately large (40 cm) with very short arms. It is a polyandrous species, meaning that males only mate with one female, but females mate with many males. It is a good mating system for researchers interested in mate choice and sperm competition (oh yeah, there’s a whole subdiscipline of the science of sperm competition – rethinking your job now aren’t you?). These have been shown to drive sperm evolution (yes, that’s a thing) and morphology to optimize fertilization success. Because in this game, it’s all about how many babies you have.

One of the things that makes this squid species particularly interesting is the dimorphism among males. Large “consort” males do all the work. They compete with other males, court females with colorful body displays, and guard the female until she spawns his offspring. Smaller “sneaker” males are just that: sneaky. They rush in under the nose (or beak, as it were) of the consort male, attach their spermatophore and book it on outta there. The dimorphism in males is reflected in their mating as well as their size. Consort males place their spermatophores inside the female’s oviduct, while the sneaker males just stick it onto the external body surface near to the seminal receptacle near the mouth. It isn’t as close to the eggs, but it must be a successful otherwise why do it? What is it that makes this stick-and-ditch strategy so successful?

To find out, the researchers dissected consort and sneaker males to recover their spermatophores. Then sperm were released into test tubes, diluted and tagged with fluorescent labels (each type with a different label). They observed that when the sperm suspension was drawn into a capillary tube the sneaker, but not the consort, sperm aggregated (or “swarmed”) to form a regularly striped pattern along the tube. And, when sneaker and consort sperm were mixed, still only the sneaker sperm swarmed. The sperm weren’t slowing down or sticking together, so what was causing the swarming? It’s not like the sperm are problem solving. So the next thought was: Maybe it’s a chemical response. So a filter assay was designed where two chambers were separated by a filter so fine that only small molecules could get though. A sperm suspension was put into the lower chamber and then each type of sperm added to the top to see where it swam. Again, only sneaker sperm migrated toward the filter. Okay, so it must be some kind of chemical attractant, but what and how?

Again, labeled sperm suspensions were put into capillary tubes. Then bubbles of different gases were microinjected into the solution. This assay revealed that carbon dioxide (CO2) attracted sneaker, but not consort, sperm. This CO2 is likely generated by the sperm via the carbonate system. Not exactly a super-simple system. To tease apart the mechanism, they developed caged carbonate (you’re thinking Han Solo…me too, but not quite the same) to sculpture gradients of bicarbonate (a basic solution, pH-wise). This system allowed them to determine that swarming depends on acidic (CO2 and/or H+) gradients but not on a biocarbonate gradient. Next, they found that carbonic anhydrases (CAs) are involved in swarming as CO2 sensors in cells.

But let’s go back to the acid thing (as both CO2 and H+ increase acidity). The researchers used a pH-sensitive dye to look at the acid gradient during swarming. They observed that the middle of the swarm acidified first, producing a H+ gradient outwards. When they added a buffer, the swarming disappeared. When they put a pipette of acid (H+) into the suspension, both sneaker and consort sperm moved toward it. But remember that only CO2 attracted the sneaker sperm. Additionally, the pH at which these types of sperm responded was different. They found that only sneaker sperm lowered their intracellular pH with environmental pH. This means that only sneaker sperm have a H+ transport system that allows for the CO2 attraction. And finally, they showed that calcium (Ca2+) influx controls cause the sperm to turn around when they reach the end (weak part) of the gradient.

Whew! That’s a lot of compact information! So let’s put it together in a whole-organism, what-the-heck-is-going-on kind of way. Why does it matter that sneaker sperm like CO2? Remember back to the placement of the spermatophores by each of the males. When the female releases her eggs, the consort male’s sperm has first access because it is in the oviduct. They fertilize a lot of eggs but not all. Then the female holds her eggs in her arms while she swims to a good substrate to release them. Squid arms and mouth are not all that far away from each other. This is when the sneaker male sperm goes to work. The swarming allows the sperm to stay close to the site of egg deposition and may be sensing CO2 released from the eggs; both increase the chances of fertilization. And, in the end, that’s what it’s all about.



Hirohashi, N., Alvarez, L., Shiba, K., Fujiwara, E., Iwata, Y., Mohri, T., Inaba, K., Chiba, K., Ochi, H., Supuran, C., Kotzur, N., Kakiuchi, Y., Kaupp, U., & Baba, S. (2013). Sperm from Sneaker Male Squids Exhibit Chemotactic Swarming to CO2 Current Biology, 23 (9), 775-781 DOI: 10.1016/j.cub.2013.03.040


And for a little more info, here's an earlier study on the same topic:


Iwata, Y., Shaw, P., Fujiwara, E., Shiba, K., Kakiuchi, Y., & Hirohashi, N. (2011). Why small males have big sperm: dimorphic squid sperm linked to alternative mating behaviours BMC Evolutionary Biology, 11 (1) DOI: 10.1186/1471-2148-11-236



(image via MarineBio.org -- Note that this species is Loligo vulgaris, the European squid. It is weirdly difficult to find images of L. bleekeri, but this image gives you some of the characteristics of the genus.)

The Boob-Resource Hypothesis: Why Is Bigger Better?

It has been quite a while since I've made an entry in to the "Groundbreaking science - men like boobs" category.  In the past, I've made the following statement on this topic: "Men like big breasts, therefore women evolve larger breasts. It's an evolutionarily solid argument, assuming of course that male preference exerts any pressure on the evolution of female secondary sexual characteristics." Indeed, evidence is mounting that humans have a great propensity to rely on their perceptions of attractiveness to make mate choices. Body size, leg length, hair color and length, skin tone, and various facial features have all been studied as important attractiveness traits. But now the big question: what about boobs? If you talk to men, any men really, then you'll find that they like to look at breasts, any breasts really. But you will also probably discover that all breasts are not equal in the eyes of men. The range of breast sizes that men prefer can range dramatically. Why is this?

If we go back to my "evolutionarily solid argument" then perhaps, my "men like big breasts" statement may include an untested assumption that larger-is-better. Hmmm...well, let's think about this. Men find boobs attractive because evolution finds them attractive, boobs providing (unconscious) information on health,  nulliparity, age, sexual maturity, and/or fertility. Okay, I'll buy that. But we aren't exactly hunter-gatherers anymore. Evolutionary pressures are likely different in post-industrial societies, right? The conclusion of most of the studies on this question circles back to our original category of "groundbreaking science - men like boobs."

A newish study, published in PLoS ONE, looks at this question again. The authors take the time to point out some problems with the other studies in this area. Not that they are wrong but namely the inconsistencies in the presentation of the boobs. For example, when men are presented with computer-generated boobs (usually from one angle only) then they are found to like medium to large sizes. The authors also point out that previous studies haven't fully accounted for within- and cross-cultural differences. For example, commitment-phobic, sexist males like bigger boobs. But also, that men living in resource (food, money, etc.) limited regions also prefer larger breasts. Is this an all-men-like-big-boobs issue or is this a evolutionary, bigger-boobs-mean-access-to-more-resources issue? To get at this, the authors broke their big study down into two parts.

Study 1: Does your socioeconomic status affect your preference for breast size?

The authors went to the state of Sabah, Malaysia, on the island of Borneo. This state is one of the least developed, lowest average income area in the country. However, it is also a highly uneven area, with large disparities in socioeconomic status. The researchers recruited participants from Kota Kinabalu (high economic status), the township of Ranau (medium), and three villages in the West Coast Administrative Division of Sabah (low). These participants were asked to self-assess their BMI and socioeconomic status compared to other Malaysians (less secure, same, more secure). To evaluate attractiveness perceptions based on breast size, the researchers created rotatable 3D animations of female figures that had characteristics closely matched to the ethic group studied. They set the breast size of the figure at five cup-size levels. The participants were then asked to view a figure and rate it on a survey.

The researchers found medium breast size to be most attractive in Kota Kinabalu and Ranau but that Ranau like bigger ones than Kota Kinabalu. In the rural villages, large breasts were found to be more attractive than they were in the other two areas. When the results were examined a correlation was found that indicated that lower financial security was associated with a preference for larger breast size. These results add evidence towards what I'll call "the boob-resource hypothesis."

Study 2: Do hungry men like larger breasts?

Study 1 has an important limitation: inter-regional differences. If you combine the results of rich sexist men with poor patriarchal men then you possibly end up with a natural confound that limits your conclusions. One way to fix this is to limit your participants to the same environment and then focus on a particular dimension. In this case, the researchers chose a proxy for resource security: hunger. This choice is based on previous work that has indicated that hungry men rate heavier female body size as attractive. It is hypothesized that that this "insecure or threatening" state causes men to idealize more mature physical characteristics that signal the ability to handle a threatening environment. Okay, I can go with that I guess. The idea is that the hungrier the man the bigger his attraction to large breasts. So the researchers recruited British white men (as ethnicity matters in this kind of study) from the University of Westminster as they entered and exited a dining hall during dinner. These participants were asked for their demographic information and then asked to report their hunger on a 7-point scale. The researchers then asked only those men that reported the two hungriest and two most satiated responses to continue. Then the participants were asked to rate a set of 3D animations of female figures (like in Malaysia just changed to British characteristics). The researchers found that hungry men rated larger breasts as more attractive. These results support the other body size work as well as these researchers' Study 1 results. It appears that we can add even more support to the boob-resource hypothesis.

Okay, so what does all of this mean? Let's consider that the human female is the only primate that has permanent, full-form breasts when not pregnant. Breasts consist mostly of adipose tissue (a.k.a. fat), and fat is energy. If breast size is a reliable indicator for calorie reserves then resource-limited males should like larger breasts. The authors found support for this for both long-term (socioeconomic) and temporary (hunger) situations. However, look at other parts of a woman's body and you'll notice that the breasts are not the only areas that store fat, and that breast size is correlated with body mass. So more study needs to be done on the relative importance of breast size and body size, respectively, as indicators.

Read the full study (for free!) here:

Swami, Viren, & Tovée, Martin J. (2013). Resource Security Impacts Men’s Female Breast Size Preferences PLoS ONE, 8 (3) DOI: 10.1371/journal.pone.0057623




(image via Wikimedia Commons)

What Hurts Worse?

The science of pain presented as a very interesting question. Which hurts worse: childbirth or getting kicked in the testicles?

Admit it, you've always wondered.

Getting a Date for Valentine's Day: A Scientific Approach (Part 2)

Welcome to Part 2 of Getting a Date for Valentine’s Day: A Scientific Approach. This will make sense if you haven’t read Part 1, but to enjoy the full impact of this V-Day themed explosion of scientific knowledge, I suggest you read both. If that cramps your style then here’s a summary: (1) Just Ask, (2) Get Your Foot in the Door, and (3) Gaze Without Being Creepy. Now, let’s move on…

4. Make Them Laugh

How often do you hear that what people really want is someone with a sense of humor? Yeah, pretty often. There is some evidence that humor is related to sexual attraction, that people with a good sense of humor are preferred as friends and partners. This is especially true when men exhibit a sense of humor or use humor in their social interactions with women. A study published in 2010, again, by Nicholas Guéguen, looks at the sense of humor at the initial stages of a relationship. Does a man’s sense of humor make him more desirable to a woman he approaches to ask out? This study included young women sitting alone in the sidewalk area of different bars. Guéguen had male confederates sit near a woman and, so she could overhear them, start a benign discussion about their summer jobs. After three minutes of this some of the men would switch to a “Humor Condition” where one man in the group would tell three funny jokes while the other men at his table praised his humor. While this script was playing out, the confederates would take note if the woman was laughing or not. After his other confederates left, the joke-teller (or non-joke-teller in the No Humor condition) would then approach the female and say, ““Hello. My name’s Antoine. I noticed you when I arrived here. I just want to say that I think you’re really pretty. I have an appointment now, but I was wondering if you might give me your phone number. I could phone you later, and we could have a drink together someplace to get to know each other.” He would then wait 10 seconds while smiling and gazing at the woman to see if she gave him her number. Afterwards, the woman was asked to participate by answering a questionnaire. Guéguen found humor to “positively affect a woman’s interest in a man who expresses a sense of humor.” Additionally, higher sociability and intelligence was associated with the humorous male. Attractiveness was found to be insignificant between the Humor and No Humor groups. If we are connecting the dots then perhaps if humor = intelligence, intelligence = high status and success, high status and success = attractive to women, then attractiveness to women = humor. It’s simple logic really.

Guéguen, N. (2010). Men's sense of humor and women's responses to courtship solicitations: an experimental field study Psychological Reports, 107 (1), 145-156 DOI: 10.2466/pr0.107.1.145-156

5. Red is Sexy, Wear Something Red

I tend to think of red as an overly commercialized Valentine’s Day ploy. And it is. But, as it turns out, there may also be some actual, scientific validity to the color of love. In nature, red is often a warning color (a prey-on-me-and-die adaptation) but with humans (and some other species, like primates), red may serve as an aphrodisiac, carrying a sex and romance connotation. I’ve come across two studies, one about men the other about women, that help shed some light on this “romantic red” hypothesis. Let’s start with the men. A study published by Andrew Elliot and Daniela Niesta in 2008 investigates this red-sex link for men’s evaluation of women. Their experiment was relatively long, but to boil it down, they asked men to rate photos of women, examining whether or not the presence of red affects attractiveness. The results showed strong support for the “red effect.” Even a brief glimpse of red was shown to enhance men’s attraction to women. Red was found to enhance sexual attraction but not general positivity and characteristics (likeability, kindness, intelligence).

Now for the ladies. A study published in 2010, also by Elliot’s group, investigated how red influences how women view men. For women, red has been linked to love and passion, carrying the meaning of sex and romance. Okay, got it, red equals attractive, right? Well…women are complicated creatures, and study upon study has shown that women don’t just take something as simple as attractiveness into account when choosing a partner. They also look for such things as authority, wealth, and status. But research has shown that red is linked to strength, power, high status, and competitive dominance, appearing historically as symbols of these traits. Put together, this means that the color red should enhance women’s attraction to men by increasing their perception of the man’s status and therefore her attraction to him. That is exactly what Elliot et al.’s study tested. Again, I’ll boil down their long experiment: They asked female participants to respond to a photo of a man. These photos were manipulated for color in either the background or on the clothing of the man. The results showed that women who viewed men with red (background or clothing) perceived him to be more attractive and were more sexually attracted to him. Women who viewed a man wearing red also perceived him to have higher status and higher status potential, and women who viewed a man described as high in status perceived him to be more attractive. What did we learn from these studies? That red is a sexy color for both men and women, so try a little red in your wardrobe.

Elliot, A., Niesta Kayser, D., Greitemeyer, T., Lichtenfeld, S., Gramzow, R., Maier, M., & Liu, H. (2010). Red, rank, and romance in women viewing men. Journal of Experimental Psychology: General, 139 (3), 399-417 DOI: 10.1037/a0019689
 
Elliot, A., & Niesta, D. (2008). Romantic red: Red enhances men's attraction to women. Journal of Personality and Social Psychology, 95 (5), 1150-1164 DOI: 10.1037/0022-3514.95.5.1150

6. Say it With and Near Flowers

Show your love, give them dying flower genitalia. Setting aside the fact that a bouquet of flowers is just a bunch of reproductive organs, flowers are used to reflect our emotions and moods, usually in a positive way and especially with women. Given this, a study by (you guessed it!) Nicholas Guéguen in 2011 examines how women respond to men with flowers. He wanted to know if physical attractiveness, sexual attractiveness, and dating potential would be influenced by the presence of flowers. He found that the simple presence of flowers in a room was enough to have women show more interest towards a man, and women who were exposed to flowers were more likely to say yes when asked out. Guéguen published a follow-up study in 2012 where he had men approach and ask out women in a shopping mall. He found that women approached near a flower shop were more likely to accept a date than women approached near other types of stores. So, as it turns out, flower genitals really are your ticket to love, or at least a first date. Perhaps you shouldn’t mention the word “genitals” though.

Guéguen, N. (2011). ‘‘Say it with flowers’’: The effect of flowers on mating attractiveness and behavior Social Influence, 6 (2), 105-112 : 10.1080/15534510.2011.561556
 
Guéguen, N. (2012). “Say it … Near the Flower Shop”: Further Evidence of the Effect of Flowers on Mating The Journal of Social Psychology, 152 (5), 529-532 DOI: 10.1080/00224545.2012.683463

We have come to the end of our sciency guide to solicitation (the legal kind) success. What have we learned? You should stake out some flowers (I never said you had to buy them) in your red shirt, skirt, tie, or whatever. Then you should tell a good joke before walking up to your potential date and opening with a unique request, segueing into an offer of a date. Simple, right?

Obviously this isn’t the be-all and end-all to this discussion (or Nicholas Guéguen would be out of a job), and so if you have any other studies you love on this topic please share them in the comments below.

Happy Valentine’s Day!


(image via staggered)

Getting a Date for Valentine’s Day: A Scientific Approach (Part 1)

Quite frankly, most years I feel like kicking Valentine’s Day in the truffles. Do I recognize this as a single woman’s reaction to a mushy, lovey, couples' holiday? Sure, but the urge to kick remains. This year, however, I’ve decided to take a more lighthearted, less violent approach. Part of this approach is to recognize, and even revel in, the more ridiculous aspects of commercialism and human relationships. As such, I found a selection of papers that, when put together, loosely instruct on how to get a date for Valentine’s Day (or any day really). As I started writing I realized that it would be just mean to make this a single post. I’d have people unsubscribing and falling asleep (not necessarily in that order) before they got through the second paper. So I’ve divided this “guide” into two parts.

1. Just Ask 

To get a date you must first find someone who is willing to date you. A paper published in the Archives of Sexual Behavior in 2011 by Nicholas Guéguen takes a look at how gender plays a role in receptivity to sexual offers. Guéguen conducted his study in France, gathering male and female university students to act as confederates. These confederates were first rated on their attractiveness using a 9-point attractiveness scale. Then they were asked to approach potential partners of the opposite sex on the street and say “I find you very likeable and attractive.” After this, the confederate asked one of two randomly determined questions: “Will you come to my apartment to have a drink?” or “Would you go to bed with me?” This study found that “men were apparently more eager for sexual activity than women” and that they were more willing to go to an unfamiliar female’s apartment and bed than females were when asked the same questions. You are completely shocked, I can tell. Forty percent of females agreed to go to an unfamiliar male’s apartment, and only one agreed to the sexual offer. These were the same results found in a similar study in the United States, supporting the idea that these reactions aren’t just typical of Americans. The U.S. study, however, did not take attractiveness of the solicitor into account. Guéguen’s experiment found that the more attractive the solicitor the more likely they were to get a positive answer, and that solicitor attractiveness was more important for males than for females. Women were more likely to go for a drink with an attractive man, but that attractiveness had no impact on the sexual offer. The men were more likely to say yes in general and even more likely to say yes to an attractive woman. You’re shocked again I can see. The take home from part 1 of our Valentine’s Day Guide? Perhaps, it is that asking doesn’t hurt. They may say yes, especially if you’re hot.

Guéguen, N. (2011). Effects of Solicitor Sex and Attractiveness on Receptivity to Sexual Offers: A Field Study Archives of Sexual Behavior, 40 (5), 915-919 DOI: 10.1007/s10508-011-9750-4
 
2. Get Your Foot in the Door 

We can’t argue that the first point/instruction was blunt. Very blunt. So then, let’s refine it a bit. Nicholas Guéguen’s group also published a paper in 2008 about the “foot-in-the-door technique.” In this study, once again conducted in France, male confederates first asked a woman one of two foot-in-the door questions: “Hello, I’m sorry to bother you but would you have a light for my cigarette?” (note: In France, the rate of female smokers is higher so this isn’t a weird question) or “Hello, I’m sorry to bother you but I am looking for the Place de Libération.” If she responded to his question he then said “Thank you very much. Are you busy now? If not, we could have a drink together, if you have some time.” Guéguen found the foot-in-the-door technique to be associated with a greater number of positive responses to the second, courtship-related question. I’ll also point out that the men did not ask the women to go back to a strange apartment and/or jump into bed with them. Probably also a plus. A new, similar study published in 2012 by Dariusz Dolinski, looked at that initial foot-in-the door request, asking if the type of foot to put in that door matters. Dolinski had male and female confederates assigned to three different conditions: no initial request, a typical initial request, or an unusual initial request. The results showed that the “uncommonness of the first, initial request may enhance the effectiveness of the foot-in-the-door technique.” The author suggests that an unusual request requires the respondent to think about why they are complying, looking at themselves and the solicitor more closely. If we put together the blunt, just-ask technique with this second technique then we can conclude that asking is better than not asking and that a unique (and I’ll add: not creepy) lead-in is beneficial in gaining a yes for a date.

Gueguen, N. (2008). Foot-in-the-door technique using a courtship request: a field experiment Psychological Reports, 103 (6) DOI: 10.2466/PR0.103.6.529-534
 
Dolinski, D. (2012). The Nature of the First Small Request as a Decisive Factor in the Effectiveness of the Foot-in-the-Door Technique Applied Psychology, 61 (3), 437-453 DOI: 10.1111/j.1464-0597.2011.00477.x
 
3. Gaze Without Being Creepy

Eyes are small but important features. You can tell a lot from someone’s eyes. They guide our attention to objects that are important, have aesthetic value, or both. Did you know that attention strongly varies as a function of how attractive a person is? It’s true. It has been shown that both men and women gaze longer at more attractive opposite-sex faces. Now, that seems relatively common sense, but if you look at gazing as a signal of mate quality then you have a whole new pick-up technique in your repertoire. But your gender and how long you gaze matters. You don’t want to be the creepy-starey-person or the weird-shifty-eyed-person. A study published in the Archives of Sexual Behavior by Ischa van Straaten et al. in 2009 investigates to what extent the length of people’s gazes during social interactions is affected by the attractiveness of the partner. They recruited University students, put them in a naturalistic bar-like environment, introduced confederates and participants, seated them face-to-face, and filmed them with hidden cameras. After a conversation, the participants were led to a different room, where they rated the confederate’s attractiveness and their own dating desire. The results of this study showed that “the expression of attraction through gazing in real-life interactions varies between men and women” with men gazing longer at attractive women than less attractive women and the length of women’s gazes to be unaffected by attractiveness. The authors suggest this is because “men engage in overt, proactive, mating strategies while women engage in more covert, cautions strategies.” Granted, this study just looks at gazing rather than making suggestions for dating. But if we use this knowledge to make conscious decisions about how we (literally) look at someone then the conclusion for this technique would be to look at someone (especially male to female) a little bit longer to show that you find them attractive. Practice with gaze length may be required so as not to squick her out.

van Straaten, I., Holland, R., Finkenauer, C., Hollenstein, T., & Engels, R. (2009). Gazing Behavior During Mixed-Sex Interactions: Sex and Attractiveness Effects Archives of Sexual Behavior, 39 (5), 1055-1062 DOI: 10.1007/s10508-009-9482-x

That's all for now. Look for a Part 2 on Wednesday!

(image from Arkadin blog)

The Science of the Friend Zone

I'm liking some of the things posted over on YouTube by Vsauce. He poses some interesting and funny questions and then tackles them in an entertaining and informative manner. Here's his video on The Science of the Friend Zone. What do you think about his conclusions?

Hey, I Could Be Your Girlfriend

In the immortal words of Avril Lavigne: “Hey hey, you you, I don't like your girlfriend / No way, no way, I think you need a new one / Hey hey, you you, I could be your girlfriend...”

Do I need to apologize for subjecting you to that? I almost feel as if I do. But it serves my point, I swear. Let’s say that the song was not titled “Girlfriend,” but instead was called “Mate Poaching.” Admittedly, it doesn’t really have the same ring to it, but that is essentially what she’s talking about.

Human mate poaching is when someone tries to attract another person who is already in a relationship. This special form of attraction comes in both the short-term (the casual sexual dalliance) and the long-term (“If they only knew we were soul-mates!”) varieties. You can also look at it from different perspectives, the poacher or the poachee. In the latter, you have what is called mate poaching enticement where the person in the relationship is trying to attract someone new. Regardless of the duration, the interaction involves at least three people in a complex web of emotions, conflict, and sex (usually secretive sex). Put that together and you’ve got one good psychology study and several mediocre movies on your hands. Think about it: Romance, attraction, competition, persuasion, deception, jealousy, betrayal. It’s like the Hollywood checklist. But, being a science blog and this coming from a science paper, we’ll stick to the psychology study part.

Now, I’ve done quite a few posts on relationships. Most of these have to do with the attraction of one sex to another. Today we look at the other end of the relationship. A slightly older paper published in the journal Personality and Social Psychology Bulletin delves into mate poaching enticement. How do you attract someone when you have this extra relationship component? Studies have shown that it is the same way you attract someone otherwise. Men tend to like beauty and sex, and women like the resource acquisition and dominance. You’re shocked, I can tell. However, mate poaching has several unique aspects or tactics. For example, targeting the mating rival and manipulating that emotional commitment. It also has costs that range from a blemished reputation to an all-out physical smack-down from the offended party. This paper looks at the former, the tactics, that people use to elicit a poaching attempt on themselves. The researchers do this by separating their study into two studies:

Study 1: What tactics do people use to entice another into making a mate poaching attempt? 

A preliminary study was conducted to identify and name mate poaching enticement tactics so that they could be rated for effectiveness in the main study. In the main study, they gave participants a sheet of paper asking for their sex and containing an instructional set. These instructions explained mate poaching enticement, gave a list of tactics compiled from the preliminary study, and asked the participants to rate the acts on a 7-point scale. They found that already-mated men who were seeking a short-term relationship had the most luck using the tactics “Enhance Potential Mate” (boost their ego, compliment them, tells them they deserve someone better), “Use Humor”, and “Provide Easy Sexual Access” (offer sex, ask for sex, make a pass). If a man is seeking a long-term relationship then his best tactics are “Enhance Potential Mate,” “Be Generous” (show you are a caring person, be extra polite, help with work or chores), and “Use Humor.” The researchers found that already-mated women seeking a short-term relationship had the best luck when the “Arrange Easy Sexual Access” (appear naked in room or car, turns a friendly date into a romantic one, suggests casual sex only), “Enhance Potential Mate,”, and “Provide Easy Sexual Access” tactics were employed. So, offer sex and thou shalt receive sex? Yep. For women seeking a new long-term partner, the best tactics were to “Develop Emotional Closeness” (confide in them, be good friends, talk about interests), “Mention Looking for Replacement,” and “Be Generous.” Overall, they found that enhancing an ego and being generous worked the best.

Study 2: What tactics do men and women use to disguise mate poaching enticement? 

People tend to use deception tactics to gain access to things that they want. Often these tactics both increase the deceiver’s perceived value while also hiding their intentions from the competition. You can probably see how this is useful in the scope of mate poaching enticement. Again, the researchers conducted a preliminary experiment to identify and name these deceptions and disguise tactics so they could be rated later. As with the previous study, they gave a set of participants an instructional set, asking them to rate on a 7-point scale how effective each tactic would be at hiding from a current partner the fact that someone is trying to attract a new partner. They found that women were seen as more effective when they used the tactics “Keep Things Normal” (don’t change physical look, keep daily routine), “Use Friends” (introduce new partner to a faithful friend, friends help in the cover up, continues to go out with friends), “Lie About Relationships” (future plans, family involvement), "Lie About Self” (lie about past, lie about ending current relationship, keep conversation routine), “Establish Independent Self” (open bank account in own name, separate credit cards), and “Social Isolation” (attend fewer events, don’t discuss new partner, don’t spend much time away from work or home). In contrast, men were more effective when they used the tactics “Decrease Time with Current Partner” (goes out less with current partner, avoid being alone with current partner) and “Use Work Excuse” (work more hours, extra projects, sneak away from work). In terms of social level, when deceiving a community it is best to use the “Distance Friendships” (stop hanging around with mutual friends, don’t tell anyone about new partner, think before speaking in public) tactic, but when deceiving a single person it is best to use “Phone Tactics” (give new partner a fake phone number, buy new cell phone, get separate line). Overall, it was found that the effective acts for men were those that showed others that his current relationship would continue unabated, providing his mate with a close emotional connection. For women to be most successful at deception they must show that they maintain their daily routine. Apparently acting as if nothing is different or even increasing romance and sex with her mate are especially effective in disguising a mate poach. Put simply: blind him with sex.

The more I read through this paper the more I felt like I was reading Science’s Guide to Cheating and Getting Away With It. I can’t say that any one thing in this study was particularly surprising. I don’t know if it is because it truly is predictable or if it is because we’ve all heard these excuses before. Hard to tell really. What do you think?

David P. Schmitt, & Todd K. Shackelford (2003). Nifty Ways to Leave Your Lover: The Tactics People Use to Entice and Disguise the Process of Human Mate Poaching. Personality and Social Psychology Bulletin, 29 (8), 1018-1035 DOI: 10.1177/0146167203253471

The Mother-in-Law Conflict

Your mother-in-law. And the need she feels to help you raise your kids. Blame menopause. And evolution.

Humans are a cooperative breeding society. We live in extended family-groups in which both "breeders" and "non-breeders" contribute in rearing the offspring. However, humans are one of the select few species (including pilot whales and killer whales) that are known to stop reproducing long before we die. This means that a significant proportion of this cooperation includes non-breeding helpers in the form of post-menopausal women. As with most things in science, there are hypotheses that to try to explain this structure. Two of these are the Mother and Grandmother Hypotheses. Basically, they say that reproducing late in life is costly but that there are indirect benefits to increasing the reproductive success of your offspring. That makes sense when looking for reasons for the evolution of menopause, if you are going to die if you have late-in-life babies then it is probably beneficial to remove the ability to do so. But the reality is that, in humans, the death risk is only 3 percent before menopause, and that's in societies lacking modern medicine. So maybe there is another reason. Enter the inclusive fitness theory. This is often used to describe social insect societies and non-sterile helpers in cooperative breeding invertebrates. However, this theory typically ignores age-specific reproductive overlap between generations of females. Mix a little game-theory modeling in there and you get the Reproductive Conflict Hypothesis. This postulates that the conflict between mothers and their adult offspring selects against late-life reproduction which may, in turn, select against increasing ages of fertility. Perhaps now would time to point out that in this case we are not talking about the shouting-match kind of conflict, but rather the reproductive conflict between generations.

A new study, published this week in Ecology Letters, tests the hypothesis that this conflict between genetically unrelated generations of women (which I will name and heretofore call the mother-in-law conflict or MILC <--that's a good one right?!) could have promoted the evolution of menopause. Are you are causing your mother-in-law to become sterile? Evolutionarily speaking, of course. The authors of this study used a large data set from Finland that cataloged birth, death and marriage records kept by the Lutheran church between 1702 and 1908. They wanted to know if MILC really exists, what the consequences of it are, and which hypothesis best explained the evolution of menopause.

The researchers found that MILC is an important component. They found that the chances of children dying increased when mothers-in-law and daughters-in-law gave birth around the same time. The simultaneous reproduction of these generations was associated with a decline of 66 percent in offspring survival. Additionally, the children of the older women had 50 percent lower survival. Those are pretty large numbers which suggests that it is highly beneficial for the mothers-in-law not to have children. When using the inclusive fitness model, they found that when the in-law generations reproduced at the same time, there was a strong selection against women remaining fertile after age 51. So which hypothesis explains these changes in inclusive fitness? As it turns out, the Reproductive Conflict Hypothesis and the Grandmother Hypothesis contributed about the same while the Mother Hypothesis had no real effect. Essentially, there are more benefits to being a grandmother (and presumably helping raising your grandchildren) than there are in continuing to have children late in life. However, this study does not address the topic of plasticity in maintaining the ability to conceive late in life or the physiological explanations for the evolution of menopause. As always, more study is needed.

Mirkka Lahdenpera, Duncan O.S. Gillespie, Virpi Lummaa, & Andrew F. Russell (2012). Severe intergenerational reproductive conflict and the evolution of menopause Ecology Letters, Article first published online: 22 AUG 2012 DOI: 10.1111/j.1461-0248.2012.01851.x

Also:
Nature News article "In-law infighting boosted evolution of menopause"

The Art of Animal Lovin'

Animal mating systems explained using cute human art.

(via diviantART)

Bring on the Stupid

Have you ever tried to talk to a guy when he's talked to a pretty woman? It's like talking to a brick wall. He's got eyes, and other parts, only for her. If a bomb were to drop at his feet he might not even notice. It is so common an occurrence that books and movies frequently feature men who are trying hard to impress a beautiful woman and in so doing manage to be at their clumsiest, most forgetful, and dumbest. So I suppose that it was only a matter of time before there was a study about it.

A couple of previous studies have shown that men's cognitive performance is depleted after a short interaction with an attractive woman, particularly if the man is trying hard to impress her. This behavior has been shown to be taxing on the brain because they are trying so hard to control and manage their behavior. Merely anticipating an interaction with a woman can render a man virtually brain dead. Then there's what are called "pseudo-interactions" in which a man and woman do not communicate face-to-face (telephone, Internet, texting, etc.). In our technologically advancing world, these pseudo-interactions are becoming more and more commonplace. Anticipating an interaction and pseudo-interactions are similar in that men frequently know little to nothing about they woman they are (or will be) corresponding with, and if they have not yet met he has no idea if she is attractive or single or whatever. One of the aims of the paper in today's post was to determine if men's cognitive performance decreased after one of these pseudo-interactions with a woman. The second part of the study looked at anticipation and a man's motivation to make a good impression.

The first experiment expected that men would perform worse on simple tasks after a pseudo-interaction with someone of the opposite sex than after a pseudo-interaction with someone of their own sex. They found that women were not influenced. Men, however, showed a decline in cognitive performance after interaction with a woman even though there was no actual face-to-face contact, and they didn't even know what she looked like. The second experiment expected that men (but not women) would perform worse at simple tasks if they anticipated a mixed-sex interaction than if they anticipated a same-sex interaction. Again, females were not influenced. They found that just the anticipation of interacting with a woman influenced a man's cognitive performance, and it wasn't in the positive direction.

What did we learn from this study? Something as small as mentioning a female name instead of a male name is enough to make men dumber (at least temporarily). Add to that, sitting in the same room with a woman, talking to her on the phone, chatting with her online, or just anticipating that he might meet up with a woman is enough to render a man thinking-impotent.

Guys, it's truly amazing you function at all.

Read the complete study here:
Nauts, Sanne, et al. (2010) The mere anticipation of an interaction with a woman can impair men's cognitive performance. Archives of Sexual Behavior: published online 01 November 2011. (DOI: 10.1007/s10508-011-9860-z)

Gaydar: A Scientific Approach

I've been hearing about some studies recently on various podcasts and news outlets and decided to look them up and see what they were all about. Studies about how people perceive other people are, in my opinion, interesting if often difficult to quantify. Perception, in an evolutionary and/or social context, can be very useful in informing an individual about potential enemies, friends, or mates. The topic of today's post focuses on the latter.

There has been some recent evidence that people are capable of extracting information from nonverbal behaviors and the appearance of other people. The most important social cues are those from the face. Think about it. We recognize faces more accurately than we do most other parts of the body. We can also classify individuals into groups just by looking at their faces. With just a glimpse we can tell identity, emotional states, sex, age, race, etc.

Today's post looks at an article recently published in Psychological Science concerning the perceptions of women to the sexual orientation of men. Studies have shown that gay men tend to make more accurate judgements of sexual orientation than do straight men. This may be due to in-group effects of perception and memory. Similar studies have shown that women tend to be better judges of nonverbal behavior than men are, and that extroverts are better judges of peoples' traits than are introverts. How can we boil this down to a biological, mechanistic explanation? How about fertility? Women can categorize male faces faster than female faces at higher periods of fertility. Also, when they are nearer ovulation, they rate masculinized faces and body gaits as more attractive. Conversely, lesbian women categorize female faces faster than male faces at periods of higher fertility. Today's paper takes a look at women's accuracy in judging male sexual orientation during various points in their fertility cycle as it potentially has sexual relevance. To test this the researchers broke their study down into three parts:

Study 1:
This first study hypothesized that women nearer to peak ovulation would be more accurate in judging male faces. Participants included heterosexual women who were not using any contraceptive medications and who reported regular cycles. They presented these participants with photographs of gay and straight men and asked them to judge sexual orientation. The women were then asked questions to judge where in their cycle they were currently at. The results showed that the women's accuracy was significantly greater the closer they were to peak ovulation. Perhaps this is because a woman's success in conceiving is greater the nearer she is to peak ovulation, and therefore she needs to have greater accuracy in identifying a suitable mate for reproductive success.

Study 2:
The procedures for this study were identical to those in Study 1 with the exception that the participants viewed the faces of 100 lesbian and 100 straight women and asked to judge sexual orientation. The hypothesis here being that ovulation would not affect the categorization of sexually irrelevant women's faces. The results showed that the women's accuracy was not related to their fertility when they judged these other women. Based on this it appears that the link between fertility and accuracy only applies to men. This is consistent with the reproductive success hypothesis suggested in Study 1.

Study 3:
This study used experimental manipulation to examine women's accuracy in judging sexual orientation. To do this they compared the judgements of "women primed with a mating goal" with the judgements of "nonprimed control" women presented with male faces and female faces. What is the first thing you think of when yu read that sentence? Me? It's how do you prime a woman with a mating goal? First, get your mind out of the gutter please. The researchers had the women read a story which "described a romantic encounter." Ok, so I didn't actually look up the story they used but I'm picturing that typical bodice-ripping poolside paperback that so many women are apt to read. Anyway, after reading the story the women were asked to judge faces. The results showed that these primed women were significantly more accurate in judging men's sexual orientations than women who had not been primed. However, this priming had no effect on the accuracy of the judgments of women's sexual orientations.

Overall, these studies suggest that "a disposition toward mating increases heterosexual women's accuracy in detecting the sexual orientation of members of the opposite sex." Basically, hitting on a gay man gets a straight woman nowhere so her gaydar needs to be accurate for her to find an appropriate mate.

Here's the paper:
Rule, Nicholas O. et al. (2011) Mating interest improves women's accuracy in judging male sexual orientation. Psychological Science: 22(7), 881-886. (DOI: 10.1177/0956797611412394)

For additional information on perceptions take a look at the research and publication list of the first author of this paper:
http://www.psych.utoronto.ca/users/rule/

(image from codeproject.com)

Boom Boom Pow

First, I've gotta say, if spiders can be cute then jumping spiders are the cutest. For today's entry, I'm redoing an older video post about jumping spiders, expanding on it and including the papers that go along with it.

Jumping spiders belong are classified as Arachnida: Araneae: Salticidae. They are easily distinguished from other spiders by the four big eyes and four small eyes on the top of their head. They hunt by spotting prey from a distance, sneaking up on it, and then pouncing. Hence, there name. They are also known for their creative, and often entertaining, courtship dances. The males dance before the females, displaying their dancing talents, their coloration, and their overall sexiness. If the female likes the dance then she will choose that male to mate with. A good dance will also inhibit her predatory tendencies, meaning she won't eat her suitor.

Before we get to the actual study, first take a look at this short video of a male jumping spider (Habronattus tarsalis) performing a courtship dance (sorry, embedding has been disabled for this video so you'll have to click the link):

http://youtu.be/UTbHpV_zFjE   (or click HERE)

There are a probably few things that you noticed right away: (1) he moves his pedipalps throughout his dance, (2) he moves around a lot while quickly moving his front legs, (3) "touchdown!" arms, and (4) there is no sound on this video.

The article that is the focus of today's post takes a look at #4 as it relates to all the other numbers. It is known that many types of spiders use substrate-propagated vibration as a kind of signalling. A good example of this are the vibrations propagated through the webs of orb-weaving spiders. Other spiders use water, soil, leaf litter, or plants. There are three types of substrate-born vibration production mechanisms that have been described in spiders: percussion (drumming body parts against a substrate), stridulation (rubbing two rigid body structures together), and vibration (oscillation of body parts coupled to the substratum). Jumping spiders are unique in that they are "visual specialists." Their very good sight coupled with the vibration makes for a good display.

Before reading about the study, take a look at the courtship display, this time with sound:



Male and female Habronattus dossenus were the test subjects of this study. Females were anesthetized with CO2 and tethered to a wire with wax on a substrate of stretched nylon fabric. Then they dropped the males onto the nylon and allowed them to court the female freely. The courtship was video recorded, and they recorded the substrate vibrations with a system that allowed them to measure the velocity of the moving surface.A total of 20 different males were recorded, using the same tethered female. Then the researchers analyzed the videos frame by frame and created power spectra for the analysis of the vibratory signals. Next, they put together the signal manipulation experiments. For this the substrate floor for courtship was a sheet of graph paper attached to a square cardboard frame. Again, the females were tethered and the males allowed to dance. The courtship ritual was videotaped, and the males seismic signals were recorded by placing a piezo-electric sensor directly underneath the female. That way they could test exactly what she was "hearing."

From the video they were able to break down the courtship into four distinct phases:
Phase 1 -  Sidling movements where the male approaches in a "zigzag" visual display, waving his forelegs and spreading his pedipalps
Phase 2 -  The male comes to within one body length of the female and produces rapid "downbeat" gestures
Phase 3 - Multiple bouts of prolonged signalling
Phase 4 -  The male attempts to mount the female

Additionally, seismic displays were found to only occur in phases 2 to 4. These seismic displays were broken down into three broad categories: thumps, buzzes, and scrapes. Thumps occur when the forelegs are raised high above the body in a nearly vertical position and are then rapidly slapped down onto the substrate, producing a percussive impulse, and also producing an air-borne sound. Then the forelegs return to vertical and the abdomen is pulled back and then released, causing it to "ring," a brief, high intensity signal. Scrapes occur in groups, between thumps. They consist of up-and-down movements of the tips of the forelegs followed by dorso-ventral oscillation (rocking motion) of the abdomen. Buzzes occur alone in Phase 3 and are always preceded by 2 to 5 thumps. Here, the front legs come down in slow continuous movement while the abdomen produces a sustained, rapid, low-amplitude oscillation. These signals are last a long time and their frequencies are temperature dependent.

Overall, when the researchers combined the seismic and visual display data they found the courtship dances to be very complex. They found that the seismic signals produced by the male corresponded to the movements of his abdomen but not of his forelegs. If they prevented the abdominal movements they found that it effectively "silenced" the males with out affecting their visual or percussive displays. These abdominal signals match the frequency characteristics of the buzz but not the thump or the scrape. Therefore, there is no timed coordination of the visual and seismic signals. That means there is not a common production mechanism, seismic signals are produced independently of visual signals.

Why evolve multiple signals? The authors pose two "quality-based" hypotheses. Females are looking for strong, healthy males that carry good genes that they can pass along to their offspring. Because they can't see genes directly they must find another way to assess the males' condition. Signals. The first hypothesis is that of the "backup signal." This is when different signals provide the same information about the sender but allow for a more accurate assessment of the sender's condition. In the case of jumping spiders, this would mean that the visual and seismic signals are alternative media for the same signal information. If visual signals are obscured then seismic signals become very important. This would be more plausible if the spider were courting at night (which it does not), if the female were far away (which she is not), or if chemical cues were produced (which they are not). Perhaps the three seismic signals are backups for each other, if the substrate the spider is dancing on does not carry one form of signal it will carry the others. The second hypothesis is that of "multiple signals." This is where different signals code for different aspects of the sender's condition. This is, perhaps, the better hypothesis. Male jumping spiders are strikingly ornamented, especially the body parts they use for courtship. Coloration is something that females are often attracted to as well as predators. If a male can survive even when he is easy to see then he must have good genes right? In this case, the three different seismic signals could also be relaying multiple messages, especially since they are produced by different anatomical structures. Likely telling the female that these structures are working like they are supposed to.

See what I mean? Complicated.

This is the study:
Elias, Damian O. et al. (2003) Seismic signals in a courting male jumping spider (Araneae: Salticidae). The Journal of Experimental Biology: 206, 4029-4039. (DOI: 10.1006/anbe.2003.2245)

If you like this one here's another study with web building spiders:
Maklakov, Alexei A., Trine Bilde, and Yael Lubin (2003) Vibratory courtship in a web-building spider: Signalling quality or stimulating the female. Animal Behaviour: 66(4), 623-630. (DOI: 10.1006/anbe.2003.2245)

Some websites where you can learn more about jumping spiders:
Salticidae (Aranae) of the World and Monograph of the Salticidae (Araneae) of the World by Jercy Proszynski
Tree of Life page on jumping spiders by Wayne Maddison
Jumping Spiders of the World

Some movies of jumping spiders HERE (click on "videos" on the left side of the screen) and jumping spider courtship HERE

And a fun story about "Dirty Dancing" spiders from over at NPR:
http://www.npr.org/blogs/krulwich/2011/05/05/135963961/dirty-dancing-a-gallant-spider-goes-all-the-way

(first image from the linked NPR story, credited to Thomas Shahan)

Happy Guys Finish Last

James Dean

Finally, science has figured out the romantic pull of characters such as Heathcliff (Wuthering Heights), Edward Rochester (Jane Eyre), and even Edward Cullen (Twilight) and James Dean, among others. It's all in those brooding expressions.

A new study in the journal Emotion examines the relative attractiveness of various facial expressions. In general, showing a happy face is considered essential to friendly interactions (including sexual attraction) but few studies have actually looked at whether or not a happy expression is, in fact, attractive. Think about it. What kind of facial expression is attractive in the opposite sex? A smile, confidence, pride, appeasement, neutral? After all, you can tell a lot by a person's expressions; they are indicators of a person's dispositional qualities. Previous studies have shown that pride signals express a high social status and that shame, an appeasement display, signals low social status. Studies have also shown that happiness communicates friendliness, approachability, and some measure of trust. That makes sense, but is the attractive expression the same in men and women? Up till now the research suggests that women tend to seek partners who are reliable providers and that men seek partners that are young, healthy, and receptive. In terms of facial expression that would translate to women seeking pride and men seeking happiness. This paper discusses two studies used to test this.

Study 1: This first study tested the prediction that the effect of emotion expression on attractiveness would vary by gender. A total of 184 Canadian undergraduates were approached by an examiner (of the same gender) holding a photograph of an opposite sex target posing with an expression of happiness, pride, shame, or neutral. Using a 9-point scale, the participants were asked to view and judge the image based on how sexually attractive they found the person in the photo. Controlling for absolute gender differences (standardizing ratings within gender to equate male and female means), happiness was found to be more attractive in women than men, pride was more attractive in men than women, and of the lesser attractive expressions shame was found to be more attractive in men than in women.

Study 2: The first study used only one male and one female in their photos and so the participants could have been responding to the unique features of those individuals. This second study addresses that by including multiple people across photos, portraying each expression, that had been gathered from the Internet. This study was further broken down into groups of people: Sample A and Sample B and Sample C. Sample A were undergraduates who viewed and rated 80 photographs (20 of each expression: happiness, pride, shame, neutral). Then they completed a Socio-Sexual Orientation Scale that measured the individual differences in mating strategies. Basically, it tested whether the effect of an expression on how you viewed a target's attractiveness varied if you view the target as a potential short-term or long-term partner. Sample B consisted of adults recruited through social networking websites who were asked to view and rate the attractiveness of photos. This time, though, it was of 40 photos, 10 of each gender showing each expression. Sample C were undergraduates who viewed and rated the same set of photos viewed by Sample B. The results showed that male pride was the most attractive male expression and female happiness was more attractive than pride. Surprisingly, male happiness was rated as one of the least attractive expressions by most participants.

Overall, this research shows that men are made most attractive by displaying pride and least attractive by displaying happiness whereas women are most attractive displaying happiness and least attractive by displaying pride. The shame expression was found to actually increase the attractiveness of both men and women, at least compared to a neutral expression. So, well, why? Here's what the authors suggest --

Pride: In males, "the pride expression may convey heightened masculinity...and may signal a man's competence and ability to provide for a partner and offspring" while in females "the mate value of a high-status women is more ambiguous" as males "seek female partners who [are] best equipped to bear children, but not necessarily to support them." This is evolutionarily speaking, of course, as contemporary men did not rate pride expressions as unattractive, just less attractive than happiness.

Shame: In females this expression fell between happiness and pride. The assumption with a shame expression is that the individual is of low-status and "submission connotations increase its apparent femininity, and thus the attractiveness of shame-displaying women." That women who express shame are "signalling the respect for social norms and the awareness that she has violated them" (what I would probably call the I've Been a Bad Bad Girl Hypothesis), and what the authors say may indicate trustworthiness. In men the shame display was more attractive than happiness. That one is difficult to explain. The authors postulate that "shame's communication of trustworthiness and group commitment" is the reason behind it's attractiveness rating. Ya know, maybe it is that coy, slightly suggestive look that gets peoples' boosters going.

Happiness: This expression usually consisted of a nice big smile :-) In men, happiness was rated very low, perhaps because a happy expression gave the "appearance of femininity and low dominance" In women the expression is a "friendliness signal...taken to indicate sexual receptivity, [increasing a] woman's mate value." It is one of friendliness, trustworthiness, and approachability. All things that men like when on the prowl for the ladies. After all, a male signalling that he is sexually receptive...uh, duh.

So guys, adopt that brooding, prideful, no-smile policy when lookin' for your next girl. Of course, some romantic wind-swept moors would be to your advantage. Just...leave the vampire body glitter at home.

Here's the paper:
Jessica L. Tracy and Alec T. Beall (2011) Happy guys finish last: The impact of emotion expressions on sexual attraction. Emotion: published online 23 May. (DOI: 10.1037/a0022902)

I was first turned on (no pun intended) to this by an article I read online. Here are a few links to sites that have covered this paper:
http://www.cbc.ca/news/yourcommunity/2011/05/smiling-men-study-do-women-prefer-bad-boys.html
http://www.reuters.com/article/2011/05/26/us-smiles-sex-idUSTRE74O5ZT20110526
http://www.huffingtonpost.com/2011/05/25/brooding-men-smiling-wome_n_866979.html

Fishy Codependency

Angler fish belong to the order Lophiiformes. They are deep sea fish named for their unique way of luring in their prey. They have a long filament that extends from the top of their head, near the eyes and mouth, that is movable (some even have tips that can light up!) and so can be wiggled to imitate prey. It acts as bait to bring in smaller creatures, like a fishing lure, and when the curious, hungry critter gets close the angler fish strikes. The topic of today's post, inspired by the comic below from The Oatmeal, is about angler fish reproduction. Some angler fish, particularly the Ceratiidae, have one of the most unusual matings systems you'll find in the animal kingdom.

This story is completely true.

(click on comics for a larger view)

(Comic via The Oatmeal)

Some additional internet sources on angler fish:

http://deepseacreatures.org/anglerfish

http://www.environmentalgraffiti.com/animals/news-post-mortem-impregnation-and-other-weird-habits-angler-fish

http://www.thesea.org/TheSea/deep_sea_angler_fish.html